The present invention relates to a process for operating an electric machine and a driver system for an electric machine.
German patent document DE 198 35 576 A1 discloses a driver system for a permanently energized electric motor in which the driver system includes a driver arrangement for driving power electronics and an operating state detection arrangement for detecting an operating state of the driver system and/or the electric motor. If the operating state detection arrangement detects the presence of at least one predefined operating state, then the driver arrangement generates a command for producing a short circuit between all the connections of the electric motor. The predefined operating state is a fault state which includes at least the following faults: dropping off or failure of a motor supply voltage, faults in the area of a motor position sensor, faults in the area of a current sensor for detecting the current flowing in at least one phase, short circuit faults (in particular in the area of the motor), or increase of an intermediate circuit voltage over a predefined limit value.
The number of electronic components in motor vehicles is constantly increasing. Consequently, the complexity of the networks used in motor vehicles, or of the cross-linking of components, is increasing. For example, drive-by-wire systems have increased the number of electronic components in motor vehicles. This increase in electric components and cross-linking requires a careful monitoring of the functionality of the components and of the networks associated with them.
It is thus an objective of the present invention to provide a method for operating an electric machine with a driver system which monitors the functionality of the relevant components, and in given cases, engages suitable measures to avoid undesirable consequences. In particular, it is an objective of the present invention to ensure the reliability of the parameters relevant to safety. It is another objective of the present invention to provide a device for carrying out the method.
The present invention includes a method for operating an electric machine with a driver system, in which an operating variable of the electric machine or the driver system is monitored. The validity of the input variables of the driver system may be checked in parallel in two independent function blocks. A fault reaction may be produced, if at least one of the two function blocks determines that the input variables are invalid.
By checking the validity of the input variables, incorrect input variables may be detected. Input variables are customarily transmitted from a network to the control unit. The network can, for example, be based on a CAN bus, on MOST, on a light conductor bus, or on a FlexRay communications system. Transmission errors can occur, e.g., due to a transmission path which is faulty and/or subject to interference. The transmitted input variable, also called a message, can be incorrect or out-of-date. In the control unit itself, the input variable can be stored incorrectly, due to faulty memory modules, in particular ROM faults or RAM faults. Furthermore, operating errors can occur. For example, network commands may be executed incorrectly or an incorrect network command may be executed. The input variables are then designated as valid, if they are current and without transmission errors. In particular, information concerning whether the input variables are up-to-date and a checksum may be checked. The two validity checks may be processed in the same time window. Therefore, there are two independent, simultaneous checks. A fault is considered as recognized if one of the two checks recognizes a fault. Accordingly, the reliability of the input variable being up-to-date and freedom from error of the input variables thus checked can be increased.
In another exemplary embodiment of the present invention, a moment mode, a charging mode, and a rotary speed mode are provided. In particular, the electric machine can be operated in these modes. Naturally, other modes can also be provided. This has the advantage that the electric machine can be adapted precisely to the behavior desired by a user. In the charging mode, the electric machine is regulated so that an effective charging of a battery can be achieved. In the moment mode, the moment is intended to be regulated. In the rotary speed mode, on the contrary, the rotary speed is the variable which should be held constant or varied according to the wishes of the user.
In another exemplary embodiment of the invention, a maximum and a minimum permissible moment are generated, depending on the operating mode of the electric machine. In each operating mode, the loadability of the electric machine is different. If the limits of the permissible moments are determined depending on the mode of operation, the result corresponds better to the values which can be realized without damaging consequences. The mode-dependent limit values are more precisely adapted to the state of the electric machine and the needs of the user, where incorrect loads are avoided and the permissible operational range is utilized in an optimal manner.
According to another exemplary embodiment of the invention the permissibility of an actual moment of the electric machine is checked in a stepwise comparison with respect to several comparison variables. Thus, a precise checking of the actual moment for permissibility is possible with high error recognition. All the conceivable limits and impacts can be taken into account. The results of the different checks may be combined to form one result. Also, the results of the different comparisons can, in given cases, be compared and correlated to one another still further.
According to another exemplary embodiment of the invention, the permissibility of an actual moment of the electric machine is checked in a parallel comparison to several comparison variables. Here, all the results may be supplied independently of one another to one or more function blocks operating as a fault reaction unit.
The device for carrying out the method starts from a driver system for an electric machine, in which the driver system includes a control unit and a monitoring unit. According to the present invention, the monitoring unit includes an adapter for adapting input variables of the control unit to the operational parameters of the electric machine and/or a checker for checking the permissibility of the state variable of the electric machine.
By the permissibility of a state variable of the electric machine being checked, faults or faulty processes, also called process plane faults or function plane faults, can be determined within the control unit. Likewise, a faulty inverter or an inverter operating in a faulty manner and/or a faulty or not completely functional electric machine can be detected.
A fault may be defined as non-satisfaction of a requirement for a certain unit or of a certain unit. Double faults may be defined as two faults which occur within a short time window or time period and have no causal connection to one another. Duplicate faults may be defined as two faults which occur outside of the short time window and also have no causal connection to one another. Advantageously, these types of faults can, to the extent that they lead to deviations in the theoretical states, be discovered by the method according to the invention. Obviously, the foregoing enumeration of the types of faults is not exhaustive and, with the method according to the invention or the device according to the invention, other types of faults, e.g., causally connected faults, can be recognized.
The method according to the present invention can be integrated in a simple and straightforward manner in control units or control devices customarily provided in motor vehicles. Thanks to the high reliability of the method, corresponding electronic components or signals/variables can be monitored and evaluated rapidly. Consequently, a fault reaction can also be initiated immediately in order to avoid damage to electronic components and endangering the safety of the user. The method according to the invention may be implemented by software technology.
The monitoring of the corresponding components or signals and, in given cases, the initiation of the fault reaction or suitable measures is done autonomously, i.e., independently of a user reaction or, when used in a motor vehicle, independently of a reaction of the driver.
The method according to the invention or device according to the invention can advantageously be used in complex networks with a plurality of electronic components.
These and other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.